A known seating area adjuster disclosed in U.S. Pat. No. 7,614,693 B2 (hereinafter referred to as Reference 1, see FIGS. 1 to 8) includes a seating member forming an outer shape of a seat cushion, a support member supporting the seating member, and an adjustment mechanism fastening thereto a front end portion of the seating member. The adjustment mechanism is moved in a longitudinal direction of a seat by a movement mechanism relative to the support member while being rotated around a rotation shaft by a rotation control mechanism. The rotation shaft extends in the width direction of the seat cushion. Thus, the front end portion of the seating member is moved to thereby adjust the outer shape of the seating member. Consequently, a length of the seat cushion (seating surface) is adjusted, for example, depending on a physical attribute of a seated occupant so that his/her femoral region is appropriately supported by the front end portion of the seating member. In addition, the seating area adjuster is arranged at each of right and left sides in the width direction within the seat cushion while having a symmetric structure in the width direction. Accordingly, an operation of the seating area adjuster will be described below with reference to one of the right and left sides of the seat cushion.
According to Reference 1, the rotation control mechanism includes a guide pin and a guide hole that is formed at a flat surface portion of a guide bracket fixed to the support member. The guide pin fixed to the adjustment mechanism slides along the guide hole of the guide bracket in accordance with the longitudinal movement of the seating member, thereby moving the adjustment mechanism in an adjusting direction relative to the support member. A large slide resistance may occur between the guide pin and the guide hole; therefore, the seating area adjuster requires a large operating force to rotate the adjustment mechanism. As a result, an electric motor serving as a source of power requires a large torque. Moreover, it is necessary to secure a high strength (rigidity) of the guide bracket in which the guide hole is formed to therefore increase the size of the guide bracket, for example, an increase of a thickness of the guide bracket.
In addition, the movement mechanism that is the so-called X-link is described in a modified example of a first embodiment (in a second embodiment) of Reference 1. In the case where the X-link is applied, it is required to increase lengths of levers (bar members) of a link mechanism in order to increase a moving direction of the adjustment mechanism relative to the support member in the longitudinal direction of the seat. As a result, the size of the movement mechanism is increased. Similarly as described above, the large operating force to rotate the adjustment mechanism is required for the seating area adjuster.
A need thus exists for a seat cushion adjusting apparatus, which is not susceptible to the drawback mentioned above.